Electric valve system for dynamoelectric machines



Oct. 21, 1941. E. E. MOYER 2,260,046

ELECTRIC VALVE SYSTEM FOR DYNAMOELECTRI C MACHINES 7 Filed Dec. 1, 1939 2 Sheets-Sheet 1 Fig. I.

SYN CHRONGUS MO TOR 0R DENSER TAGE CONTROL CIRCUIT Inventor: Elmo E. Moger,

His Attorney.

Oct; 21, 1941. E. E. MOYER 2,260,046

ELECTRIC VALVE SYSTEM FOR DYNAMOELECTRIC MACHINES Filed Dec. 1, 1939 2 Sheets-Sheet 2 Inventor: E l mo E Moyer, 0

His Aiz'borney.

Patented Oct. 21, 194.1

UNITED s 'r s- PATENT OFFICE I :2 1: 1! FOIt nrimiuo- Elmo E. Meyer, Scotia', N. Y., assignor to General Electric Company, a corporation of New York Application December 1, 1939, Serial No. 307,068

12 Claims.

My invention relates to electric valvesy'stems and more particularly to control or protective systems for electric valves employed asexciters for dynamo-electric machines.

Electric valve apparatus has been iound'very satisfactory for energizing the field windings of dynamo-electric machines due tethe precision of control which the electric valves aiiord, By using electric valves of the controlled type whereby the average current conducted or the average output voltage is accurately controllable, it is possible to obtain precise control of operating characteristics of dynamo-electric inachines. The use of electric valve means in sys-' tems of this nature has made it necessary to develop new and improved control circuits to fa-.

cilitate the use of electric valves in these systems.

In accordance with the teachings of my invention described hereinafter, I provide new and im-f a modification of the arrangement of Fig. 1 in which the protective apparatus is, connected to or associated with the main or power electric valves. r a

Rei'erring now .to Fig. i or the accompanying drawings, my invention is there illustrated as applied to an electric valve systemior energizing the field-winding: of adynar'n'o-electric machine suchas a synchronous condenserl. The synchronous condenser l. comprises a plurality of armature windings 2' and a-field winding 3. In order to start the synchronous condenser I, I provide a source 4 oi -alternating voltage of reduced valu which may be" connected. to the an s mature windings 2 duringthe startingoperation by means or a circuit breaker; 5.;' DuringnormaI operation, the armature-windingsl are connected to an alternating currents-circuit of normal or nominal voltage, v

When startingthe syn hrbnous condenser las an induction motor, I provide meansior shunting the field winding 3 during thest'arting operation. I

This shunting means may comprises. resistance 1 and a pair of normally closed contacts 8 which are connected in ,seriesrelation across the terminals oi the field winding 3. The contacts 8 may be operated by a suitable time delay relay electric valve apparatus which is employed as an exciter for the field winding of a synchronous condenser.

Briefly stated, in the illustratedembodiments of my invention I provide new and improved electric valve exciters for' energizing the field Winding of a synchronous condenser. The system in-' cludes protective apparatus to maintain the electric valves nonconducting during a part of the starting sequence and to assure connection of the exciter. to the field winding at a precise time during the starting sequence.

For a better understanding of my invention,-

reference may be had to the following description 9 arranged to open with a time delay but arranged to closesubstantially coil Ill. The alterhating current circuit breaker 5 may be provided with an auxiliary switch ll having a contact l2 which is open and maintained open during the oiI and starting positions oi the breaker 5 and closed in the running position, so that the actuating coil in is energized from a suitable source pi current, such as a battery l3, in the running position of the breaker 5.

I provide an electronic or electric valve exciter for energizing the field winding 3, and the exciter comprises an inductive network including a' transformer 14 having a plurality of primary windings l5 and a plurality of secondary windings L6. The exciter'also includes a plurality of v main or power electric valves l1, l8 and i9 which taken in connection .with the accompanyingdrawings, and its scope will be pointed out in the appended claims. Figs. 1 and 3 diagrammatically illustrate embodiments of my invention as applied to an electric valve exciter for energizing the field winding of a synchronous condenser inwhich the main electric valves are provided with are preferably of the type employing an ionizable medium and each comprises ananode 20, a mercury pool cathode 2i and a make-aliveor immer- ,sion ignitercontrol member 22, The immersion igniter control members 22 are each of semi-conducting material such as=boron-carbide or silicon-carbide and have an extremity thereof immersed in the associated mercury pool vcathodes trigger or control electric valves and in which the protective apparatus is associated with thecontrol valves. Fig. 2 diagrammatically illustrates 2!. The electric valves are renderedconductive. by the transmission of current of a predetermined value through the control members: I employ open position.

a plurality of excitation circuits including control electric valves 23-25. The control electric valves 23-25 ar also preferably of the type employing an ionizable medium and each comprises an anode 26, a cathode 21 and a control grid 28 and a shield grid 29 which may be connected to the cathode. A suitable transient voltage absorbing means, such as a capacitance 30, may be associated with each of the control valves. The control electric valves 23-25 are each connected to be responsive to the anode voltage of its associated power valve.

A suitable switching means 3| may be connected between the transformer i4 and a suitable source of alternating current 32 to effect energization of the exciter. Of course, if desired, the exciter may be energized from the alternating current circuit 5. The switching means 31 is biased to the open-circuit position and provided with an actuating coil 33 and also includes a pair of auxiliary contacts 34 which are arranged to be closed when the switching means Si is in the The actuating coil 33 may be energized from any suitable source of current, such as a direct current source 35, through a time delay relay 36 and a switch 31. Switch 31 and switch H may be mechanically interconnected so that switch 31 is closed in the starting and running positions of the circuit breaker 5.

I employ a suitable or conventional voltage regulating circuit 38 for controlling the conductivities of the control valves 23-25 and hence to control the energization of the field winding .3 in response to the voltage of circuit 6. limiting resistances 38' maybe connected in series relation with the control grids 28.

As a means for preventing transmission "of current by the main valves Il-IS and the control 7 valves 23-25 duringthe. starting operation in which the synchronous condenser-1 isoperating sition. That is, switch 5| assures that current will be transmitted to the field winding 3 when the circuit breaker 5 is in the running position, even though a transient in armature current may be caused when circuit breaker 5 is changed from the starting to the running position.

Th operation of the embodiment of my invention shown in Fig. 1 will be explained by considering the system during the initiation of operation of the synchronous condenser l. Prior to the operation of the circuit breaker 5, it will be understood that since the contacts 8 of the relay 9 are normally closed, the field winding 3 of the condenser I will be short circuited through the resistance 1. Furthermore, since the switching means 3| is in the open-circuit position, the auxiliary contacts 34 thereof will be closed, effecting energization of the actuating coil of the contactor 39 so that the anode-cathode circuits of the control electric valves 23-25 are not completed, thereby maintaining the control valves and the associated main power valves i'l-IS in a nonconducting condition. The actuating coil 40 is, of course, energized from the circuit 35.

To start the rotation of the synchronous condenser the circuit breaker 5 is moved to the right-hand position to connect the armature windings 2 to the source 4 of reduced voltage. Of course, the switch H is operated simultaneously therewith and the switch 31 is also closed 'at this time, effecting energization of the time delay relay 36. As soonas the source of reduced volt- Current as an induction motor and before it reaches synchronous speed, I provide protective apparatu's- 1 for maintaining these electric valves in a non- 1 conducting condition during-that period. The

protective apparatus may comprise a relay or contactor 39 having an actuating coil 40, a pair of contacts 4| for short circuiting a resistance 42 connected in series relation .with the coil 40 on pick-up, and pairs of contacts 43, 44 and 45 age is-corinectedto the armature windings 4, it will beunderstoodby those skilled in the art 'thatthesynchronous condenser will begin to rotate, operatingas an'induction motori As soon atively high valu'efiefie'cting operation of the current relay'lfl' to "close" c'ontactsfil thereby providing'an additional path" for 1 the en'ergization or theactuatingcoil 40of the contactor 39. The

i timddelay 'relaj '36" i's"ar'ranged or timed to opmined operatin condition of the condenser,

such as a current; transformer 48 and a current responsive relay 49, to effect energization of the actuating coil 40 so long as thearmature current of the condenser I remains above a predetermined value.

contacts 5! and is arranged to open with a time delay. A switch 51 may be connected in circuit with contacts 5| of relay 49 and connected to be operated in response to circuit breaker 5 so that coil 40 of contactor 39 will not be energi'zed due to a current transient which occurs after the circuit breaker 5 is in the running poerate t'p' 'eflect eni'gi'zation of the actuating coil 33 'of' switching r'ne'ans '3l' after-"closure of contacts' 5l'-'of relay 49",therebyassuringenergization'of the coil 40 0f contactor 39.

As the speed-of the synchronous condenser increases, the armature current of the condenser decreases thereby'affording-an indication of the. speed of the condenser. As the speed ofthe synchronous condenser I approaches synchronous speed and the armature current correspond ngly decreases, the relay 49 opens itscontacts 5| with a time delay, thereby effectingdeenergization of the coil 40 of contactor 39 and closing the anodecathode circuits of the trigger valves 23-25. Upon operation of the contactor 39, the control members 22'-of the power valves II-IS are energized in a predetermined order so that unidirectional currentis transmitted to resistance 1 and of the fie'd winding of the synchronous condenser I. The value of the unidirectional cur- The relay 49 is provided with an actuating coil 50 and a pair of normally open armature windings 2.

rent transmitted'is, of course, determined by the adjustment of the circuit 38, The relay 9 is adjusted to open its contacts 8 after operation of thecontactorr39 Upon completion of the above described operations, the circuit breaker 5 -is moved to the running position, thereby connecting the source 6 of nominal voltage to the When circuit breaker 5 is moved to the running position, switch 5! is opened thereby assuring that coil 40 of contactor 39 willnot be'energized even though an armaelectric valvemeans." The closing' coils 55 of contactors 52-54 are ture current transient may be caused when the higher voltage is connected to the armature terminals. Of course, switch 5| also prevents the opening of contactor 33 ii relay 49 operates in response to current transients caused by load variations. Thereafter, the electric valve exciter operates to transmit variable amounts of unidirectional-current to the field winding of the synchronous condenser to maintain the voltage of circuit 6 at a predetermined value. In the above described operation, it'will be understood that the electric valve equipment is protected during the starting operation and that the transmission or unidirectional current to the field winding 3 is initiated at a very precise point in the starting sequence of operation. Y

I have found that where the electric valves employ immersion-igniter control members and the control members are connected to the anodes of the valves, the electric valves will conduct current during the starting operation by virtue of the voltage drop appearing across the resistance I. As will be readily appreciated, if the electric valves transmit current to the field winding during the starting operation, before the directionalcurrent to the field winding.

In-Fi'g.f2there Tis'shown afmodiflcation of my inve'ntionwhic'li corresponds in many respects to the arrangement'shown in Fig.1 andcorrespond- I 'ing' elements have been assigned like reference 'numera 2, the protective niahsfii'the*el'ectric valves n-jls reconnected directly the anode-cathode 'cir'cuitsoi them'airiorpower valves ||-|9. These protective means-may constitute individual con- 1 tactors sag-suns 54' connected" in the anodecathode circuitsof powerel'e'ctric valves II-IS, respectively. Thecontactors 52-54 maybespring "biased-'to the"--opncircuit positions and each comprises a pair of' auxiliary contacts 55 which are closed when the anode contactor is in the open-circuit position 'Each of the anode contactors 52-54 also comprises a closing coil 56 and a tripping means comprising an armature 51, a current coil 58 and an independent trip coil 59. The current coil 58 is arranged to open the contactor when the current transmitted by the associated main valve attains a predetermined value. Of course, by the use of polarizing means well known in the art, the anode contactors may be made to, operate selectively in response to reverse current occasioned by arc-back of the connected to be energizedfrom the auxiliary "source'of cu'rrent'35 through a relay 6U havlng'an actuating coil" 6| and a pair of contacts 62. Whenthe coll 6| is connected to circuit through a'--current' limiting resistance 63, the

relay-60 is cl'osed to effect energization of the closin'g 'coils55'and hence closes the anode conis obtained-'bfishunting the actuating coil SI of relay by either the auxiliary contacts ,34 of switching means 3| or by means of contacts 5| of the current relay 49. After the closure of the switching means 3| and after the current decreases below the predetermined value as the speed of the synchronous condenser increases, the coil 6| isenergized thereby closing its contacts 62 and energizing closing coil 56 of the contactors 52-54. The contactors are locked in the closed positions.

In the arrangement of Fig. 2, the relay 9 is connected to be energized through a pair of auxiliary contacts 64 provided by the current relay 49. The actuating coil ID of the relay 9 is connected to be energized from the auxiliary circuit/35 through conductors 65.

The operation of the embodiment of my invention shown in Fig. 2 will be explained by con- .sidering the system during the starting sequence. Initially, of course, the switch means 3| is in the open-circuit position, effecting closure of auxiliary contacts 34. When the auxiliary contacts 34 are closed, the actuating coil 5| of relay is short-circuited so that the anode contactors 52-54 are maintained in the open-circuit position. Furthermore, the closure of the auxiliary contacts 34 of which means 3| short circuits the actuating coil I0 of the relay 9, as-

suring that the field winding 3 is short circuited through the resistance 1. After the connection of the source of reduced voltage to the armature winding 2, the current relay 49 picks up, closing contacts 5| and still further assuring that the actuating coil 6| of relay 60 is shorted. Subsequently, the actuating coil-33 of the switching means 3| is energized "and connects the transformer M to circuit 32. When the armaturecurrent decreases to a predetermined value as the speed of the synchronous condenser inlay 60 closes its contacts 62to efiect energization of the closing coils 58 of the anode contactors 52-54. Relay 80 remains in the closedcirouit position so long as auxiliary contacts 34 and 5| are open. After closure of the contactors 52-54, a unidirectional current of predetermined value is transmitted to the field winding 3 and resistance 1. After a definite time, depending upon the setting of the relay 9, the contacts 8- of relay 9 are opened. The starting operation is then completed by connecting the source of nominal voltage to the armature windings 2. In this embodiment of my invention, switch 5| which is operated by the circuit breaker 5 or in accordance with the position of breaker 5, is arranged to be maintained in the closed circuit position so long as the breaker 5 is in the running position. Accordingly, energization of coil In of relay 9 is assured to prevent closure of contacts 8 under va'riable load conditions of the condenser 9.

In the event of an overload on any one of the main valves ||-|9 or in the event of arcback of a valve, the armature member-5-l will be actuated to trip the associated anode contactor. Upon being moved to the open circuit position, the auxiliary contacts 55 will be closed to effect energization of the closing coil 56, thereby resetting the contactor.

' Fig. 3 diagrammatically illustrates another embodiment of my invention which is similar corresponding elements have been assigned like reference numerals. In this embodiment of my invention, I provide apparatus for maintaining the trigger or control electric valves non-conductive by impressing hold-oil or biasing potentials on the control grids thereof during the starting operation to assure that unidirectional current is not transmitted to the field winding 3 of the synchronous condenser. Instead of using a single circuit breaker for starting the synchronou's condenser I, I may employ a pair of circuit breakers 66 and 61 for connecting the alternating current circuits 4 and 32, respectively, to the armature windings 2. Circuit breaker 66 is provided with auxiliary contacts 68 and 69, and circuit breaker 61 is provided with auxiliary contacts 19, H and 72.

The contactor 39 in the arrangement of Fig. 3 is employed to impress suitable biasing potentials, such as a negative unidirectional biasing potential, on the control grids 28 of the control electric valves 2325 during the starting operation. Contactor 39 is also provided with an additional set of contacts 13, the function of which is to be explained hereinafter. A suitable source of negative biasing potential, such as a battery 14, may be employed to furnish the negative biasing potential.

--'Ihe auxiliary contacts 34 of the circuit breaker 3| are arranged to be closed when the breaker is in the, closed circuit position. I provide a suitable means, such as a relay 15 having an actuating coil '16 and contacts l1 and 18 to seal in the contactor 39 in the energized position so long as the current relay 49 is in the closed circuit position, thereby assuring that the control valves 23-25 are maintained nonconductive so long as the armature current transient exists. As a means for connecting the voltage regulator 38 operatively to the system and particularly to the control electric valves 23-25, I provide a relay 19 having an actuating coil 80 and a pair of contacts 8|. Coil 80 is energized through contacts 69 of breaker 66 when that breaker is in the closed circuit position. In this manner it is assured that the voltag regulating circuit is connected to the control electric valves 23-25 upon the initiation of the starting sequence occasioned by the closure of circuit breaker 66.

The operation of the embodiment of my invention shown in Fig, 3 will be explained by consid- .ering the system during the starting operation. 1

- transient occasioned by the connection of the low voltage source to the condenser I effects closure of contacts 5! of relay 49 and energizes the actuating coil 40 from circuit 35 through a circuit including the positive terminal of circuit 35 contacts 4 I, contacts 11 of relay l5, auxiliary contacts 34 of circuit breaker 3|, to the negative terminal of circuit 35, Relay 49 thereby operates relay 75 which seals in contactor 39. Upon operation of contactor 39 to the energized position, contacts 43-35 are closed connecting the negative terminal of the battery 14 to control grids 28 ofcontrol electric valves 23-25, inclusive, thereby maintaining the control electric valves. and the associated in many respects to that shown in Fig. 1 and principal electric valves ll-IS in a nonconductive condition.

' As soon as the armature current decreases to a predetermined value, the relay 49 drops out and opens the circuit for energizing actuating coil 40 of contactor 39. Accordingly, the negative unidirectional biasing potential impressed on the control grids 28 is removed and the electric valves 23-25 are in condition to transmit a predetermined value of unidirectional current to the field winding 3 and the shunt or discharge resistance 1 which is connected across the field winding 3 when contacts '13 of contactor 39 close to effect energization of the actuating coil ll! of relay 9. Subsequently, circuit breaker 61 is closed to connect the nominal or normal armature voltage to armature windings 2 of condenser I. When in the closed circuit position, auxiliary contacts H of circuit breaker 61 are closed to energize coil 80 of relay [9, thereby assuring connection of the voltage regulating circuit 38 to the control electric valves 23-25. In this manner, the amount of current transmitted to the field winding 3 during the starting operation is pre-established. Relay 9 is designed to open its contacts 8 a predetermined interval of time after energization of actuating coil ID, 'thereby removing the shunt connection across the field winding 3 and eiiecting transmission of a predetermined amount of unidirectional current to the field winding 3 by electric valves l1-l9.

While I have shown and described my invention as applied to'particular systems of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I-, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, a dynamo-electric machine of the synchronous type comprising an armature winding and a field winding, a source of current, translating apparatus for energizing said field winding from saidsource and comprising electric valve means having an anode-cathode circuit for transmitting current to said field winding, an

electric circuit, means for connecting said armature winding to said circuit to initiate operation of said machine, and means connected in the anode-cathode circuit for maintaining said electric valve means nonconducting during the starting operation.

2. In combination, a dynamo-electric machine of the synchronous type comprising an armature winding and a field winding, a source of current, electric translating apparatus for energizing said field winding from said source and comprising an auxiliary inductive network and electric valve means having an anode-cathode circuit, an electric circuit, means for connecting said armature for energizing said field winding from said source and comprising an inductive network and electric valve means having an anode, a cathode and an immersion-igniter control member, a control circuit for energizing said control member and comprising means energized in response to the anode voltage of said electric valve means, an electric circuit, means for connecting said armature winding to said electric circuit to start said motor as an induction motor, and means for preventing operation of said control circuit during the starting operation-so that current is not transmitted to thecontrol members.

4. In combination, a synchronous motor having an armature winding and a field winding, a source of current, electric translating apparatus for energizing said field winding from said source and comprising an inductive network and electric valve means for transmitting unidirectional current to said field winding, an electric circuit, means for connecting said armature winding to said electric circuit to start said motor as an induction motor, means for shunting said field winding during the starting operation, and means independent of the voltage of said armature winding and responsive to the current of said armature winding of said motorto maintain said electric valve means non-conducting during the starting operation.

5. In combination, a dynamo-electric machine or the synchronous type comprising an armature winding and a field winding, a source of current, electric translating apparatus for energizing said field windingzfrom said sourceand comprising an inductive network and electric valve means, switching means for connecting said source to said inductive network, an electric circuit, starting means for connecting said armature winding to said electric circuit to iniiate the operation of said machine, contactor means iorconnecting said electric valve means operatively in circuit with said field winding, and means for preventing operation of said switching means and said contactor means until a predetermined interval of time after the operation oi said starting means.

6. In combination, a dynamo-electric machine of the synchronous type comprising an armature winding and a field winding, 2. source of current, electric translating apparatus for energizing said field winding from said source and comprising an inductive network and electric valve means, switching means for connecting said source to said inductive network, an electric means, means for connecting said armature circuit, starting means for connecting said armature winding to said electric circuit to initiate the operation of said machine, contactor means for connecting said electric valve means operatively in circuit with said field winding, and means for preventing operation of said contactor means until the armature current or said machine decreases to apredetermined value.

7. In combination, an alternating current dynamo-electric machine of the synchronous type comprising an armature winding and a field winding, an alternating current circuit, a source of alternating current of reduced voltage for starting said machine, an electric circuit, electric translating apparatus connected between said electric circuit and said field winding for transmitting power thereto and comprising an inductive network and electric valve means, switching means for connecting said inductive network to said electric circuit, means for shunting said field winding, transmission of current by said electric valve protective means for preventing winding to said source of reduced voltage to initiate the operation of said machine, means responsive to the armature current of said machine to maintain said protective means in operation so long as the armature current remains above a predetermined value, and means for operating said switching means and said protective means a predetermined interval of time after the initiation of the energization of said armature winding.

8. In combination, a dynamo-electric machine comprising an armature winding and a field winding, an electric circuit, a source of current, translating apparatus for energizing said field winding from said source and comprising electric valve means, said electric valve means having a control member for controlling the conductivity thereof, switching means for connecting said armature winding to said electric circuit to initiate the operation of said machine, and means responsive to the operation of said switching means and responsive to the magnitude of the armature current for maintaining said electric valve means in a nonconductive condition during the starting operation comprising means for impressing on said control member a biasing potential.

9. In combination, a dynamo-electric machine of the synchronous type comprisng an armature winding and a field winding, an alternating current circuit of normal voltage, an alternating current source of reduced voltage, circuit controlling means for selectively connecting said armature winding to said circuit or to source of reduced voltage, electric translating apparatus for transmitting unidirectional current to said field winding and comprising electric -valve means having a control member for controlling the conductivity thereof, means responsive to said circuit controlling means for impressing a biasing potential on said control member to maintain said electric valve means nonconductive, and means responsive to the current of said armature winding for rendering inoperative said last mentioned means.

10. In combination, a dynamo-electric machine of the synchronous type having an armature winding and a field winding, a source of normal operating voltage, a source of reduced voltage for starting purposes, circuit controlling apparatus for selectively connecting said armature winding to either of said sources, electric translating apparatus for transmitting unidirectional current to said field winding and comprising electric val e means having a control member for controlling the conductivity thereof, a voltage regulating circuit for energizing said control member to pre-establish the value of current to be transmitted to said field winding, and means responsive to said circuit controlling means to connect said voltage regulating circuit operatively to said electric valve means.

11. In combination, a dynamo-electric machine of the synchronoustype having an armature winding and a field winding, a source of normal operating voltage and a source of reduced voltage for starting purposes, circuit controlling means for selectively connecting said armature winding to said sources, electric translating apparatus for transmitting unidirectional current to said field winding and comprising electric valve means having a control member forcontrolling the conductivity thereof, a voltage regulating circuit for age to pre-establish the value of current transmitted to said field winding. and means responsive to the current of said armature winding for maintaining said electric valve means nonconductive during the starting operation when said armature current exceeds a predetermined value 12. In combination, a dynamo-electric machine of the synchronous type having an armature winding and a iield winding, a source of normal operating voltage and a source of reduced voltage for starting purposes, circuit controlling means for selectively connecting said armature winding to said sources, electric translating apparatus for impressing on said control member a control voltwhen the armature current decreases to a pretransmitting unidirectional current to said field determined value to permit said voltage regulator to control the conductivity of said electric valve means.

ELMO E. MOYER.

CERTIFICATE OF CORRECTION. Patent No. 2,260,0h6. October 21, 19141.

ELMO E. IXOYER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, second column, line 29,after the word "substantially" insert --instantaneous- 1y upon deenergl zation of itsactuetir.5-; 3, Second column, line 20 for "switch" read -switching-; line 27, for the Word "which" read --switch-; and line 65, for "9" need "1 and that the said Letters Patent should be read with this correction therein that the samemay confonn to the record of the case in the Patent Office.

Signed and sealed this 9m day of Decanber, A. n. 19h1.

V Henry Ven Arsdele (Seal) Acting Comnissioner of Patents. 

